Automatic transmission

ABSTRACT

An automatic transmission for vehicles is equipped with a housing in which a number of clutches and brakes, as well as an input shaft and an output shaft and at least one torque-controlling shaft ( 1 ), are positioned. The torque-controlling shaft ( 1 ) is equipped with neither a lengthwise bore for the central supply of fluid to the clutches or brakes, nor cross bores and grooves.

[0001] The invention relates to an automatic transmission as specifiedin detail in the preamble to claim 1.

[0002] Torque-controlling shafts equipped with cross bores and groovesare used both in continuously variable automatic transmissions and inmulti-stage automatic transmissions to supply hydraulic fluid toindividual components of the transmission, such as torque converters andshifting components, wherein the cross bores are ordinarily designed ascylindrical bores having a transfer radius at the outlet point.

[0003] One example of this type of multi-stage automatic transmission isdescribed by the applicant in DE 199 08 840. In this case, themulti-stage automatic transmission is equipped with a number of clutchesand brakes. A torque-controlling sleeve shaft feeds coolant to a clutch,discharging it through the radial cross bores in the torque-controllingshaft. The torque-controlling shaft is also equipped with grooves forvarious gaskets.

[0004] An example of a continuously variable automatic transmissionhaving a multi-plate clutch is described by the applicant in DE 197 34839 A1. In this case as well, a primary shaft, designed as atorque-controlling shaft, is provided with cross bores for theintroduction of fluid for lubrication and cooling of a multi-plateclutch; these cross bores are ordinarily designed as cylindrical crossbores having a transfer radius at their outlet point. This primary shaftis also equipped with grooves for gaskets. It has been found thattorque-controlling shafts of this type having cross bores and grooves,used in automatic transmissions, especially in vehicles, are susceptibleto fracture under certain conditions due to a notch effect. Fracturestend to begin in the outlet area of the cross bores and grooves.Increasing the strength of these torque-controlling shafts having crossbores by improving the materials used to manufacture them, or byoptimizing the tempering process, is not economically feasible due tothe increased costs. Attempts have also been made to vary thepositioning, the number, and the diameter of the cross bores, and toreduce the notch effect by improving surface quality. In such cases, thefunction of the flow of oil required for the optimal operation of theautomatic transmission is often unacceptably restricted. In order toproduce the necessary strength levels, the torque-controlling shaftsmust be strengthened in the area of the cross bores and grooves. Forreasons of vibration technology, it is necessary for thetorque-controlling shafts to have low torsional stiffness. Butincreasing strength around the cross bores and grooves substantiallyincreases torsional stiffness. In addition, the overall diameter, andthus also the overall size of the component, are negatively affected.Furthermore, known-in-the-art torque-controlling shafts are comprised ofmany components, which require costly sealing methods. The maincomponents of these torque-controlling shafts are the turbine shaft, thestator sleeve shaft, and the flange.

[0005] The object of the present invention is to disclosetorque-controlling shafts that can be used in the central supply offluid to a torque converter and to shifting elements in an automatictransmission, in which cross bores and grooves, and the related,required increases in strength, can be eliminated, thus preventingincreases in torsional stiffness, and reducing the number of componentsrequired, the size of the unit, and leakage.

[0006] The object of the invention is attained with an automatictransmission of the type described, having the characterizing featuresof the main claim.

[0007] The present object is attained in that a reshaped turbine shaft,which has no lengthwise bore for the supply of fluid, is used in thecentral supply of fluid to the converter and to the shifting elements,and in that a stator shaft is used, which is equipped with a flange thatis connected to the stator shaft via connecting elements, or preferablyvia a molding with the stator shaft. Especially advantageous are steelcomponents that are forged or milled, as these exhibit a high level offatigue strength. With a forged stator shaft having a solid forgedflange, for example, the number of components and the overall length canbe substantially reduced since the stator sleeve shaft, the fluid feedflange, and the rectangular-section ring bushing, which in the currentstate of the art are required, can be eliminated. An insert in the formof a reshaped metal tube that contains all the fluid channels is mountedin the stator shaft. According to the current state of the art, thefluid channels used in the stator sleeve shaft and the fluid feed flangehave to be cast, at great expense. The reshaped metal tube in theinvention serves as a plug-in insert, and contains gates that ensure asealing between the fluid channels, and against the outside. The insertis preferably made of steel in order to minimize as much as possible anyoil leakage that may occur with increasing temperatures. Aluminum isfrequently used in components manufactured according to the state of theart, which can lead to increased leakage at the required temperatureranges, due to thermal expansion. The insert may also be reshaped, withfluid feed channels being located on the outside, thus preventing anyundercutting in the cast model. The turbine shaft is designed as a solidshaft and is equipped with neither cross bores nor grooves between theteething. Furthermore, no reinforcements are necessary in the area ofthe cross bores and grooves. This serves to reduce the maximum shaftdiameter as well as torsional stiffness.

[0008] Advantageous and practical designs of the invention are disclosedin the sub-claims. However, the invention is not limited to thecombinations of characterizing features specified in the claims, butadditional, sensible, possible combinations of claims and individualcharacterizing features will be obvious to experts in the field from theobject of the invention.

[0009] Below, the invention will be described in greater detail using anexemplary design illustrated in the diagrams. These show:

[0010]FIG. 1 is a partial section of an embodiment of an automatictransmission as specified in the invention; and

[0011]FIG. 2 is a section along Line A-A of the automatic transmissionas specified in the invention and illustrated in FIG. 1.

[0012] The automatic transmission illustrated in FIG. 1 is equipped witha torque-controlling shaft 1, hereinafter referred to as the turbineshaft, which is in a working connection with a turbine 4 and a clutchbody 5 via slaving teeth 2 and 3. The turbine shaft is designed as asolid shaft and has neither cross bores nor grooves between the slavingteeth 2 and 3. The central feed of fluid to clutches and brakes of theautomatic transmission is accomplished via a stator shaft 9 and aninsert 6. A sealing element, which is not illustrated here, is betweenthe turbine 4 and the insert 6. The insert contains the fluid channels 8and the gates 7, which ensure a sealing between the channels and againstthe outside. The stator shaft 9 is equipped with a flange 10, whichserves as a bearing for the clutch body 5. A converter cover 11 issituated on the turbine 4. A freewheel clutch 12, a power take off 13,and a control unit 14 are connected to the stator shaft 9.

[0013]FIG. 2 shows a section along the Line A-A, of FIG. 1, of theautomatic transmission specified in the invention. The insert 6, whichensures the supply of fluid to clutches and brakes, via a specialarrangement of gates 7 and fluid channels 8, is between thetorque-controlling shaft 1 and the stator shaft 9.

[0014] Reference Numerals

[0015]1 Shaft

[0016]2 Slaving Teeth

[0017]3 Slaving Teeth

[0018]4 Turbine

[0019]5 Clutch Body

[0020]6 Insert

[0021]7 Gate

[0022]8 Fluid channel

[0023]9 Stator Shaft

[0024]10 Flange

[0025]11 Converter Cover

[0026]12 Freewheel Clutch

[0027]13 Power Take Off

[0028]14 Control Unit

1. Automatic transmission for vehicles, comprising a housing in which anumber of clutches and brakes are positioned, with an input shaft and anoutput shaft and at least one torque-controlling shaft (1),characterized in that the torque-controlling shaft (1) is equipped withneither a lengthwise bore for the central supply of fluid to theclutches or brakes, nor cross bores and grooves.
 2. Automatictransmission for vehicles according to claim 1, characterized in thatthe central supply of fluid to clutches and brakes is accomplished via astator shaft (9) and an insert (6), wherein the insert (6) and thestator shaft (9) form all the necessary fluid channels (8).
 3. Automatictransmission for vehicles according to claim 2, characterized in thatthe insert (6) is equipped with gates (7), which, in conjunction withthe stator shaft (9), ensure a sealing of the fluid channels (8) andagainst the outside.
 4. Automatic transmission for vehicles according toclaim 2, characterized in that the stator shaft (9) is equipped with aflange (10), which is connected to the stator shaft (9) via connectingelements or via molding.
 5. Automatic transmission for vehiclesaccording to claim 2, characterized in that the stator shaft (9) and theflange (10) are produced by reshaping.
 6. Automatic transmission forvehicles according to claim 2, characterized in that the insert (6) iscomprised of a reshaped metal tube.